Method and apparatus to effect injection of fluids into a subsea horizontal tree

ABSTRACT

An apparatus for effecting injection of fluids into a subsea horizontal tree includes a fluid injection tree cap having a body with a bore extending therethrough so as to open at one end to a top of the body. An isolation valve is cooperative with the bore of the body so as to open or close fluid flow through the bore. The fluid injection tree cap is connected to the horizontal subsea tree. The horizontal subsea tree has only a single crown plug therein. The bore of the fluid injection tree cap communicates with an annulus of the horizontal subsea tree. The horizontal subsea tree has valving therein so as to selectively direct fluid from the bore of the tree cap to the annulus of the well or to the horizontal subsea tree.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. Provisional PatentApplication Ser. No. 62/371,953, filed on Aug. 8, 2016.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIALS SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to subsea horizontal trees. Moreparticularly, the present invention relates to systems for injectingfluids into such a subsea horizontal trees. Additionally, the presentinvention relates to apparatus for maintaining the dual barrier systemwithin the subsea horizontal tree.

2. Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 37 CFR 1.98

Conventional wellhead systems include a wellhead housing mounted on theupper end of a subsurface casing string extending into the wellbore. Ariser and blowout preventer are then installed. During the drillingprocedure, the blowout preventer is installed above the wellhead housing(i.e. a casing head) to provide pressure control as casing is installed,with each casing string having a hanger on its upper end for landing ona shoulder within the wellhead housing. Upon completion of this process,the blowout preventer is replaced by a Christmas tree installed abovethe wellhead housing, with the tree having a valve to enable the oil orgas to be produced and directly into flowlines for transportation to adesired facility.

The horizontal Christmas tree replaces the conventional casing andtubing heads of the generally vertical Christmas trees. The horizontalChristmas tree comprises a spool with a generally horizontal throughport mounted above and in axial alignment with a horizontal through portin the wellhead housing. The hangers for the casing strings aresupported one above the other within the bore of the wellhead housing,and the tubing hanger for the production or tubing string is supportedin the bore of the spool to suspend the production string within thecasing strings.

The vertical bore through the tubing hanger of a horizontal tree may beclosed by a wire line tool to connect the production fluid throughaligned side ports (generally horizontal through ports) in the hangerand spool for recovery and delivery of production fluid to a suitablelocation. A redundant seal may be provided by well cap installed in thetree above the tubing hanger, with the vertical bore aligned with thatof the tubing string closed by a crown plug.

Typical horizontal subsea trees contain two independently installed andtested crown plug assemblies. These crown plug assemblies can be locatedtogether in an extended tubing hanger or separately in the tubing hangerand an independently installed internal tree. These crown plugs create adual barrier system that isolates the main production flow path of thetubing hanger and the environment.

Typical horizontal subsea trees also include a small bore flow path thatconnects the main upper mandrel of the tree to the annulus portion ofthe subsea tree. There is typically one or two valves located in thisflow path so as to isolate the annulus portion of the tree to theenvironment. The annulus flow path enters the mandrel either above bothcrown plugs or sometimes between the crown plugs. The annulus portion ofthe tree is connected to the production portion of the tree throughcross-over piping and valving.

In order to facilitate injection of chemicals into horizontal tree, thecrown plugs must be removed to gain access to the production flow path.In some cases, fluid may be pumped into the annulus portion of the treedirectly from the upper mandrel into the production flow path throughthe cross-over piping without removing the crown plug. In the event thatthe crown plug is removed to facilitate injection, the proper wellcontrol and barrier philosophy must be put into place to prevent spillsto the environment.

For certain horizontal subsea trees that require more continuousinjection of fluids, it would be beneficial to remove the upper crownplug in order to expose the annulus flow path. As such, a device isrequired so as to maintain the required dual barriers in order toprovide the required secondary metal-to-metal barrier, provide thenecessary intervention to isolate the upper mandrel of the tree in orderto allow injection of fluids in the testing of the seals, and to providethe required hub connection to allow for the connection ofhose/pipe/equipment to facilitate injection of fluids into the tree capand thus into the upper mandrel of the subsea tree.

In the past, various patents have issued relating to subsea trees. Forexample, U.S. Pat. No. 5,992,526, issued on Nov. 30, 1999 to Cunninghamet al., shows a deployable tree cap for deployment on a subseaproduction hub of a subsea tree. The tree cap has a lightweight bodywith parallel planar sides and including suitable openings in slots formounting the various operating elements. A seal plate structure includesa piston connected to a seal plate having a pair of downwardlyprojecting tubular steel members for fitting within the production boreand annulus bore of the tree hub in a sealed landed position. Fluidpressure is applied to a fluid line to urge a piston and seal platedownwardly into a sealing landed position.

U.S. Pat. No. 7,677,319, issued on Mar. 16, 2010 to D. Baskett,discloses a retrievable tree cap for use in a subsea tree. The tree capis installed and retrieved using a remotely operated vehicle. Hydraulicpressure is used to lock the tree cap onto the subsea tree and to setthe tree cap seals. The tree cap is locked onto the subsea tree beforesetting the seals within the concentric bore. The tree cap includes alocking means that engages a profile within the subsea tree regardlessof the radial orientation of the tree cap. The tree cap is used tohydraulically isolate an annulus bore from the production bore of thesubsea tree. The tree cap provides for the injection of a corrosioninhibitor within a cavity of the tree cap.

U.S. Pat. No. 8,087,465, issued on Jan. 3, 2012 to Huang et al.,provides a locking tree cap for use in a subsea tree. The tree cap isinstalled and retrieved using a remotely operated vehicle. The tree capincludes the flexible collet fingers the lock the tree cap to a treespool. The deflected collet fingers are adapted to extend into therecess of the tree spool when the tree cap has been landed on the treespool.

U.S. Pat. No. 8,230,928, issued on Jul. 31, 2012 the Cuiper et al.,teaches a low-profile internal tree cap having a running configurationand a latched configuration to be selectively secured to a tree spool.The tree cap includes an inner sleeve movable between upper and lowerpositions. The movement of the inner sleeve to the lower positionsimultaneously engages a locking profile within the tree spool andenergizes a sealing element around the exterior of the tree.

U.S. Patent Application Publication No. 2014/0060849, published on Mar.6, 2014 to Pathak et al., discloses a cap system for use on subseaequipment, including a horizontal tree. The cap system includes a capassembly that has the flexibility of installation and retrieval. The capassembly includes a debris cap assembly in engagement with the capassembly. The cap assembly interface has to provide the ability toinject in bleed fluids into the main bore and an annulus bore of thesubsea tree independently and without removal of the debris capassembly.

Canadian Patent No. 2428165, issued on Aug. 12, 2008 to I. Donald,teaches a flow diverter for use through a tree cap. The flow diverterassembly has a flow diverter to divert fluids flowing through theproduction bore of the tree from a first portion of the production boreto the cap, and to diverge the fluids back from the cap to a secondportion of the production bore for recovery therefrom via an outlet. Theflow diverter is detachable from the cap to enable insertion of the flowdiverter through the cap.

It is an object of the present invention to provide a method andapparatus which maintains dual barriers against the release of fluids tothe environment.

It is another object of the present invention to provide a method andapparatus that maintains a secondary metal-to-metal barrier on thesubsea tree.

It is another object of the present invention provide a method andapparatus that effects the injection of fluids and the testing of sealswithin the subsea horizontal tree.

It is another object of the present invention to provide a method andapparatus that facilitates connection of the tree cap to external pipingin order to inject fluids into the subsea tree.

These and other objects and advantages of the present invention willbecome apparent from a reading of the attached specification andappended claims.

BRIEF SUMMARY OF THE INVENTION

The present invention is a fluid injection tree cap that comprises abody for attachment to a mandrel of the subsea tree. A bore extendsthrough the body so as to have one end opening at the top of the bodyand an opposite end opening into the mandrel of the subsea tree. Anisolation valve is provided on the body or in cooperation with the boreof the body in order to open or close the bore. This isolation valve is,in particular, positioned above the body of the tree cap. A hub isadapted to allow for the connection of piping on the side of theisolation valve opposite the body.

The present invention can further include the horizontal subsea tree. Inthis subsea tree, one crown plug has been removed. The subsea tree hasthe mandrel at the upper end thereof. A small bore flow path extendsfrom the annulus of the subsea tree to the mandrel. A tubing hanger islocated in the annulus. A lower connector is provided on the subsea treein order to connect the subsea tree to the wellhead. Valving is providedon the annulus flow paths and on the production flow paths of the subseatree in order to direct fluids from the bore of the tree cap to anannulus of the well or to production tubing or to the subsea tree. Thefluid injection tree cap is in a metal-to-metal seal with the mandrel ofthe subsea tree.

The present invention is also a method for effecting injection of fluidsinto a subsea horizontal tree. This method includes the steps of: (1)affixing a fluid injection tree cap onto a mandrel of the subseahorizontal subsea tree; (2) removing a crown plug from the subsea treeso as to expose an annulus flow path; (3) connecting the tree cap to afluid-delivering pipe; and (4) opening a valve so that fluid from thepiping flows through a bore in the body of the tree cap and into theupper mandrel of the tree and into the annulus portion of the subseatree. In the method of the present invention, fluid can then be directedeither into the annulus of the well bore or into the production side ofthe tree.

In this method of the present invention, an isolation valve is providedbetween a hub that is connected to the fluid-delivering pipe and thetree. In this method, the isolation valve is opened so as to allow fluidto flow from the pipe into the bore of the tree cap.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic illustration showing the application of the treecap of the present invention onto a horizontal subsea tree.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is shown the apparatus 10 of the presentinvention for effecting injection of fluids into a subsea horizontaltree 12. In particular, the tree cap 14 is applied onto the uppermandrel 16 of the subsea tree 12. The subsea tree 16 has a lowerconnector 18 that is secured to the wellhead 20. A tubing hanger 22 ispositioned within the bore 24 of the hanger portion of the subsea tree12.

The tree cap 14 includes a body 26 that has a bore 28 extendingtherethrough. In the preferred embodiment the present invention, thisbore is a two inch bore. However, the bore can be larger or smaller. Anisolation valve 30 is connected to the bore 28. The isolation valve 30can be manually or remotely operated. For example, an ROV actuator 32can be used with the isolation valve 30 so as to open or close theisolation valve. A hub 34 is connected to the bore 28 and located on aside of the isolation valve 30 opposite to the body 26. The hub 34allows the bore 28 to be connected to an injection system, such as afluid-delivering pipe. The cap 14 also includes a wellhead-type ofconnector 36 or similar device that locks onto the upper mandrel 16 ofthe horizontal subsea tree 12 and provides a metal-to-metal seal.

In the subsea horizontal subsea tree 12, there is illustrated in brokenlines a crown plug 38. This illustration is to show the location of thecrown plug 38 prior to removal. In actual operation, when the tree cap14 is positioned on the mandrel 16, the crown plug 38 is removed so asto expose the annulus flow path of the subsea tree 12.

The subsea tree 12 includes an annulus flow path 40 therein. An annulusworkover valve 42 extends outwardly of the subsea tree 12 and allowsfluid flow into the annulus. The annulus workover valve 42 can becontrolled or actuated by a remotely operated vehicle or can be actuatedfrom a surface location. The annulus workover valve 42 allows workoverfluids to be introduced into the apparatus 10. The annulus master valve44 is connected to the annulus and extends to the bore 28 of the subseatree 12 so as to allow annulus fluids to be delivered into the bore. Anannulus auxiliary valve 46 is also provided so as to extend to the bore24. A line 48 will extend from the annulus workover valve 42 and fromthe annulus so as to pass to the bore 28.

Production fluids can flow through line 50 from the wellhead 20, throughthe connector 18, through the hanger 22 and toward a series ofproduction valves. The first valve 52 is the production master valve soas to control the flow of production fluids outwardly of the subsea tree12. A production wing valve 54 is connected in line with the masterproduction valve 52. A crossover valve 56 allows fluids from the bore 28or from the annulus 40 to pass therethrough and into the productionfluids flowing along line 50. A production isolation valve 58 ispositioned along line 60 so as to stop the flow of fluids through theline 50. A hub 62 is formed at the end of the line so as to allow theproduction line 50 to ultimately be connected to piping so thatproduction fluids can be ultimately delivered to a surface location.

Typical horizontal subsea trees contain two independent crown plugs inthe bore 24 so as to isolate the main production flow path from theenvironment. However, for certain horizontal subsea trees that requiremore continuous injection of fluids, it would be beneficial to removethe upper crown plug 38 so as to expose the annulus flow path. In orderto maintain the required dual barriers, the externally-fitted fluidinjection tree cap 14 is installed with the necessary valving andconnection points. This fluid injection tree cap 14 provides therequired secondary metal-to-metal barrier by this locking connectionwith the mandrel 16. It also provides the necessary intervention valvesto isolate the upper mandrel of the tree. This effects injection offluids in the testing of the seals. The tree cap 14 also provides therequired hub connection system so as to allow for the connection of ahose/pipe/equipment or to facilitate injection of fluids into the treecap and thus into the upper mandrel of the subsea tree. The fluidinjection tree cap 14 can be installed permanently or semi-permanentlyin order to facilitate a single or routine fluid injection program.

In the method of the present invention, fluid injected from the tree cap14 into the upper mandrel 16 and through the annulus auxiliary valve 46will flow into the annulus portion of the subsea tree. Fluid can then bedirected either into the annulus of the well or into the production sideof the tree.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof. Various changes in the details ofthe illustrated construction or in the steps of the method can be madewithin the scope of the present claims without departing from the spiritof the invention. The present invention should only be limited by thefollowing claims and their legal equivalents.

I claim:
 1. An apparatus comprising: a fluid injection tree cap having abody with a bore extending through the body so as to open at one end ofsaid body, said fluid injection tree cap having an isolation valvecooperative with said bore of said body so as to open or close a flow ofa fluid through said bore; a horizontal subsea tree having only a singlecrown plug therein, said horizontal subsea tree having said fluidinjection tree cap affixed to an upper end thereof such that said boreof said fluid injection tree cap communicates with an annulus of saidhorizontal subsea tree; and a well connected to said horizontal subseatree, said well having an annulus, said horizontal subsea tree havingvalving therein so as to selectively direct fluid from said bore of saidtree cap to said annulus of said well or to said horizontal subsea tree.2. The apparatus of claim 1, said horizontal subsea tree having a tubinghanger positioned in said annulus of said horizontal subsea tree.
 3. Theapparatus of claim 1, said well being a wellhead, said horizontal subseatree having a connector at a lower end thereof that is affixed to saidwell.
 4. The apparatus of claim 1, said isolation valve positioned abovesaid body of said fluid injection tree.
 5. The apparatus of claim 1,said horizontal subsea tree having a mandrel at the upper end thereof,said fluid injection tree cap being connected by a metal-to-metal sealwith said mandrel.
 6. The apparatus of claim 1, said annulus of saidhorizontal subsea tree having a workover valve cooperative therewith soas to allow workover fluids to flow to said bore of said body of saidfluid injection tree.
 7. The apparatus of claim 2, further comprising: aline extending from said well and through said tubing hanger andoutwardly of said horizontal subsea tree so as to cause production fluidto flow outwardly of said horizontal subsea tree.
 8. The apparatus ofclaim 1, said valving of said horizontal subsea tree selectivelydirecting fluid from said bore of said tree cap to production tubingextending outwardly of said horizontal subsea tree.
 9. An apparatuscomprising: a fluid injection tree cap having a body with a boreextending through said body so as to open at one end at a top of saidbody, said fluid injection tree cap having an isolation valvecooperative with said bore of said body so as to open or close a flow offluid through said bore; and a horizontal subsea tree having only asingle crown plug therein, said horizontal subsea tree having said fluidinjection tree cap affixed to an upper end thereof such that the bore ofsaid fluid injection tree cap communicates with an annulus of saidhorizontal subsea tree, said horizontal subsea tree having valvingtherein so as to selectively direct fluid from the bore of the tree capto an annulus of a well or to the horizontal subsea tree or toproduction tubing.
 10. The apparatus of claim 9, said horizontal subseatree having a tubing hanger positioned in said annulus of saidhorizontal subsea tree.
 11. The apparatus of claim 9, furthercomprising: a well connected to said horizontal subsea tree, said wellhaving an annulus, said valving of said horizontal subsea treeselectively directing fluid from said bore of said tree cap to theannulus of the well.
 12. The apparatus of claim 11, said well having awellhead, said horizontal subsea tree having a connector at a lower endthereof that is affixed to said wellhead.
 13. The apparatus of claim 9,said isolation valve positioned above said body of said fluid injectiontree cap.
 14. The apparatus of claim 9, said horizontal subsea treehaving a mandrel at the upper end thereof, said fluid injection tree capbeing connected by a metal-to-metal seal with said mandrel.
 15. A methodof effecting injection of fluids into a subsea horizontal tree, themethod comprising: affixing a fluid injection tree cap onto a mandrel ofthe horizontal subsea tree; removing a single crown plug of saidhorizontal subsea tree so as to expose an annulus flow path; connectingthe fluid injection tree cap to a fluid-delivering pipe; and opening avalve so that the fluid-delivering pipe flows through a bore in a bodyof the fluid injection tree cap and into the mandrel of the horizontalsubsea tree and then flows into an annulus portion of the horizontalsubsea tree.
 16. The method of claim 15, further comprising: directingfluid from the annulus portion of the horizontal subsea tree into anannulus of a well.
 17. The method of claim 15, further comprising:directing the fluid from the annulus portion of the horizontal subseatree to a production side of the horizontal subsea tree.
 18. The methodof claim 15, further comprising: connecting an isolation valve to thefluid injection tree cap and of the fluid-delivering pipe.
 19. Themethod of claim 18, further comprising: opening the isolation valve soas to allow fluid to flow from the fluid-delivering pipe into the boreof the fluid injection tree.
 20. The method of claim 15, furthercomprising: affixing a tubing hanger into a bore of said horizontalsubsea tree.